1. Field of the Invention
The present invention relates to fastener driving tools, such as nailers and tackers.
2. Description of the Related Art
In general, fastener driving tools have magazines for storing a plurality of fasteners, e.g., nails, tacks, staples, etc., drivers for driving the fasteners, and devices (known as “idle driving prevention devices”) for preventing the operation of the drivers when all of the fasteners within the magazines have been used.
Japanese Patent No. 2,640,988 teaches a known idle driving prevention device. In this patent, a fastener driving tool is configured as a “finishing nailer”. A magazine stores a flat, plate-like nail strip comprising a plurality of small headed nails that are arranged in parallel and joined in series with each other. A pusher plate is disposed within the magazine for pushing the stored nails toward a nail driving channel, so that the nails are fed one after another into the nail driving channel in response to the driving operation.
The idle driving prevention device of this patent includes a stopper member and a stopper projection. The stopper member is coupled to a trigger that is mounted to a tool body of the nailer. The stopper member has an end portion that extends into the magazine. The stopper projection is formed on the pusher plate and is positioned within the magazine. When the last nail remaining within the magazine has been driven out (in other words, when all the stored nails have been exhausted), the stopper projection of the pusher plate moves to a predetermined position where the stopper member engages the stopper projection. Consequently, the stopper member cannot be moved and the trigger cannot be operated to actuate the driver. As a result, the idle driving prevention device can inhibit the nail driver operation.
In addition, the above patent teaches a technique to allow the pusher plate to move by a distance that is greater than a thickness of an individual nail, after the last nail has been fed within the nail driving channel and driven out of the tool (to enable detection of a possible idle driving operation). The two states, before and after the last nail is driven, can be clearly distinguished from each other based on the increased shifting movement of the pusher plate. Therefore, possible malfunctions of the idle driving prevention device can be minimized and the reliability of the idle driving prevention device can be improved.
In order to ensure a large shifting distance of the pusher plate for detecting possible idle driving operations, there has been a proposed solution to form a detection recess in the nail driving channel in a position opposing the pusher plate. Because the front end of the pusher plate can enter the detection recess, the pusher plate can be shifted by a distance corresponding to the depth of the detection recess in addition to the distance corresponding to the thickness of an individual nail. Therefore a large shifting distance of the pusher plate can be ensured after the last nail has been driven out.
However, in the known idle driving prevention device, the detection recess of the nail driving channel is positioned on the lateral side of the heads of the nails. Therefore, if thin nails, e.g. nails having a thickness of 0.6 mm or nails known as “pin nails”, that are more slender than finishing nails and are easily bendable, are adapted to be driven and stored in the magazine, the last nail that has been fed into the nail driving channel may not be properly held against the inner wall of the nail driving channel because the detection recess is positioned on the lateral side of the head of the last nail. Rather, it is likely that the last nail is bent at a portion adjacent to its head. Consequently, a nail driver may not appropriately contact the head of the last nail, and as a result, the last nail may not be properly driven.